The present invention relates to a valve for dynamic balancing of the flow rates of thermal carrier fluid independent of the fluctuations of pressure in hydraulic systems in an environment of HVAC (heating, ventilation and air conditioning) and of distribution of sanitary water and automatic regulation of the flow rate of feeding of terminal units, heat exchangers, fan coils, AHU batteries, metering units and the like.
In the scope defined, the abovementioned valves, known as PICV (pressure independent control valves) whereof a schematic representation (typical but not the only one possible) is given in the accompanying FIG. 1, are multifunction instruments typically made up of a functional unit “Δp” suitable for maintaining constant the differential pressure between upstream and downstream of a functional unit “Kv”, the latter being made up of at least one orifice whose area of passage can be made to vary up to total closure by means of manual actuation and/or by means of an actuator “M” of whatsoever kind.
Knowing that by fixing the area of passage of an orifice and maintaining the pressure differential between its upstream and its downstream constant means that the volumetric rate of flow which can pass through it is fixed, the PICV valves therefore carry out typically the following functions:    1) manual presetting of the maximum rate of flow which can transit through the open valve; maintaining of the flow rate set independently of the fluctuations of the pressures in the hydraulic system which follow the variation required or undergone of the conditions of use in the various branches of the system and of the utilities connected thereto;    2) motorised modulation of the flow rate regulated between the maximum presetting value and the other possible regulated reductions;    3) on-off function, i.e. the change from position of flow rate regulated to stop of the flow rate and vice versa, both for the purpose of energy saving and saving in maintenance, function performed manually and/or by means of an actuator.Referring to the diagram of FIG. 1, typically the functional unit “Δp” assigned to function 2), i.e. maintaining constant the pressure differential P2−P3 on either side of the regulation unit “Kv”, is made with a cut-off which chokes an orifice, cut-off actuated by a diaphragm which senses the differential pressure P2−P3: when the variations in pressures upstream of the valve P1 or downstream of the valve P3 seek to vary also the differential P2−P3, the diaphragm senses an imbalance in the design value and therefore moves the lamination cut-off which will vary the differential P1−P2 in an opposed manner so that the value P2−P3 will be restored to the design one.
This balancing of the flow rate independently of the fluctuations of the pressures, to be considered in itself known, will be described in greater detail here below with reference to the drawings of the valve according to the invention.
The functional unit “Kv” is assigned to perform the other functions 1), 3) and 4).
The function 1) of presetting is typically performed by an orifice/cut-off pair wherein the position of the cut-off relative to the orifice is made to change with manual mechanical operations, typically on installation of the valve or in any case during one-off regulation or maintenance of the system, consequently varying the area of passage and therefore the maximum rate of flow which from that time onwards may traverse it.
The function 3 of modulation of the flow rate is typically performed by an orifice/cut-off pair wherein the position of the cut-off relative to the orifice and therefore the resulting area of passage is made to change mechanically by an actuator (thermostatic, thermoelectric, electromechanical, solenoid, managed with direct feedback from the valve or remote, etc.) during the normal regime of functioning of the system so as to vary the rate of flow which may traverse the valve in order to modify in time the point of regulation of the end unit or branch controlled by the valve.
The on-off function 4) is typically performed by an orifice/cut-off pair wherein the cut-off is brought, manually or by means of an actuator of whatsoever kind, to occlude totally the area of the orifice so as to inhibit the flowing of the thermal carrier fluid to the subsequent components of the system.
Given the high number of components necessary for performing functions 1)→4) and the high cost of the raw material (normally brass), typically used for the manufacture of the valves to be mounted on pipes small in diameter whereon the greater sales are made, the tendency of producers of this type of valve is that of grouping together the functions relative to the management of the flow rate 1), 3) and 4) in the smallest possible number of orifice/cut-off pairs to the extent that one of the solutions of greatest success sees all three of these functions performed by a single orifice whereon single mobile cut-off equipment acts, as shown schematically in the accompanying FIGS. 2a and 2b, having the following features:                the end of the cut-off 1 which interacts with the orifice 2 is connected to a rod 3 to form mobile equipment 4 with respect to the valve body 5, which can translate with respect to the orifice for a given stroke length;        the mobile equipment can be made to slide between two positions of maximum and minimum opening, separated by the given stroke, both by a mechanism with manual action and by the action of any linear actuator 6 mounted integrally with the valve body;        the movement of the end of the cut-off consequent to the translation of the mobile equipment with respect to the orifice varies the area of passage available for the flow and therefore allows action to be taken on the flow rate;        when the linear actuator is in the fully open position and the mobile equipment is positioned at the position of maximum opening, the area of passage available for the flow is the maximum allowed by the valve and corresponds to the maximum presettable flow rate (FIG. 2a);        when the linear actuator is in the fully open position, by making the mobile equipment 4 translate manually with respect to the orifice by a certain portion of the stroke available (whether it can be done with the actuator 6 mounted or it has to be momentarily removed from the valve) the area of passage available to the flow is gradually narrowed, in this way limiting the maximum rate of flow which can pass through the valve or the operation of presetting is performed as per function 1) (FIG. 2b);        the end of the cut-off which interacts with the orifice also has such a geometry that once pressed by the manual actuation or by the actuator on an appropriate seat at the orifice 2 it interrupts the flow allowing the on-off function.        
Once the translation for the required presetting has been performed, having used an appropriate portion of the stroke available, the mobile equipment then has to be moved further to perform the function of modulation of the flow rate 3) wherein, in order to modulate the flow rate in time, the linear actuator mounted on the valve body further varies the position of the mobile equipment between the presetting position set and the minimum opening.
The functional limit of this solution therefore appears clear.
As illustrated in FIGS. 2a and 2b, according to one of the possible working methods, the action of manual presetting moves the end part of the rod of the cut-off equipment 4 away from the presser 7 of the actuator 6, thus making sure that during the subsequent phase of control modulating the movement of the presser no effect arises until it has once again reached the terminal end of the rod, all this however using a portion of the stroke, limited, made available by the actuator.
Therefore the stroke which can be used for the modulating regulation is reduced, with respect to the maximum one available, by the section used at presetting for the limitation of the maximum rate of flow which can traverse the valve: the regulation of the flow rate between the maximum ceiling and the minimum value allowed by the structure of the valve must therefore be distributed over a residual length which can also be very small (especially in heating systems where work is carried out with minimum flow rates), length over which the errors due to the inevitable mechanical, dimensional and coupling tolerances of the various components and of the actuator will be found to weigh increasingly in percentage terms, reducing in parallel the capacities for regulation of the valve and the precision of the regulation itself.
The valves disclosed in WO 2006/136158 A1 and WO 2009/135490 A2 represent two solutions to this problem, where regulation of the maximum flow rate takes place through rotation of two cylindrical elements whose degree of circumferential overlapping of the respective openings allows the maximum flow rate to be preset while the entire stroke of the pusher of the actuator is used for the axial translation of one of the two elements in the first case or of the entire equipment formed by the two elements in the second, permitting the further regulation of the flow rate which traverses the valve from the preset maximum value to zero. Given the complexity of the channels necessary for the passage of the fluid medium, the methodology necessary for the variation of these channels and the relative sliding seals between the cylindrical components of the sets of regulation equipment, both the abovementioned solutions can be realised only by means of very heavy and voluminous metal components which are complex to machine and therefore very costly, or by using components made in plastic material which is very sensitive to the environmental conditions as far as thermal expansions are concerned (therefore problems of precision during regulation) and of lower capacity for maintaining in time the functional features and therefore working life of the valve.
In US 2010/0170581 A1 a solution is proposed wherein, in order to supersede the state of the art and pursue the declared object of bringing the reading of the presetting outside of the zone of anchorage of the actuator, the flow rate is regulated by two separate sets of equipment, one which imposes a variation of area of an orifice to regulate the value of the maximum flow rate, the other which, using the entire stroke of the pusher of the actuator, varies the opening of a second orifice in order to modulate the flow rate. This solution, given the complexity of the mechanisms, shares the problems of the two previous solutions and presents a further one thereof: since the orifice of presetting of the maximum flow rate is separate and situated serially to that for the modulation, when it is subject to reduction of the area following presetting, the reduction of the area of the modulation orifice is not effective for the purpose of the variation of the flow until its area becomes smaller than that of the presetting orifice (water board phenomenon) therefore effectively rendering once again useless a first portion of the stroke of modulation made available by the pusher of the actuator.